This invention relates to a method of retention of carbonation in beverages in containers and more particularly, plastic containers made of polyethylene terephthalate (PET) or poly(ethylene naphthalate) (PEN) by adding a carbonic acid ester to the beverage. The present invention further relates to a composition for maintaining the desired level of carbonation in a container.
Plastic and metal containers have been replacing glass in bottling beverages where easy handling, low weight and non-breakability are needed. However, in the case of carbonated beverages in plastic containers such as PET, there is a loss of CO.sub.2 through the walls of the container and carbonation is not retained. Once a carbonated beverage product loses too much carbonation (e.g. 17.5%), it is unacceptable to sell to a consumer. A carbonated beverage as used herein is an aqueous solution having a pH in the range of about 2 to 4, and preferably of about 3, in which carbon dioxide gas in the range of 2 to 5 vol CO.sub.2 /vol H.sub.2 O, preferably 3.3 to 4.2 vol CO.sub.2 /vol H.sub.2 O has been dissolved. Flavor and sweeteners may also be added.
British Patent Specification 970,376 to Kaiser discloses a beverage with an added bactericide which decomposes to form CO.sub.2 and alcohol which are compatible with the beverage. A suitable bactericide is pyrocarbonic acid diethlylester which hydrolyzes completely in an aqueous solution to form ethyl alcohol and carbonic acid. Beverages treated with the bactericide exhibit extended shelf life. However, the rate of release of carbon dioxide is very rapid relative to the shelf-life of the beverage. Therefore, use of these agents in carbonated beverages result in a rate of carbon dioxide release substantially greater than the rate of carbon dioxide loss via permeation, and result in a pressure rise in the containers above the acceptable levels required for high quality product.
U.S. Pat. No. 3,441,417 to Feldman et al. discloses a dry beverage composition adapted to be reconstituted with water to form an effervescent beverage. An essential carbonating ingredient of the composition is an organic compound having a carbonic acid anhydride group capable of controlled hydrolysis in water to release CO.sub.2 over a period of 30 seconds to 3 minutes.
It is therefore the object of this invention to add a carbonating agent to the carbonated beverage that undergoes slow hydrolysis in the acidic aqueous medium and releases the CO.sub.2 to constantly replenish CO.sub.2 that is lost through the walls or top of the container (e.g. plastic container), thereby extending the shelf life of the beverage.